An engine or a compressor pump has one or more cylinders, each which has a number of valves needed for the proper operation of the engine. Typically, at least one valve is for an input port and one valve is for an output port. The valves are seated in an opening in the engine block such that the beveled face of the valve head mates with a like beveled face in the valve seat. Proper fitting of the two faces is important for proper operation of an engine. Over time the beveled face of the valve head becomes worn or pitted and must be either repaired or the valve discarded. The use of the present invention provides the machinery for performing the necessary grinding of the valve face and the valve stem's end so that the valve can be returned to operation within an engine.
The angle of bevel on the seating surface must be determined and set on the grinding device as a prelude to the grinding operation. The valve stem usually has a smooth area on a length of the stem between the valve head on one end and the distal end of the valve stem on the other end. The length will vary based on the valve application. The valve typically has a head, a stem and an end. The head is a round flat surface perpendicular to the axis of the stem and the head has an annular side surface (called the seating face) beveled toward the stem. The end of the valve stem opposite the head, the distal end, must be first ground flat and perpendicular to the axis of the valve stem.
The beveled seat grinding operation is accomplished by a grinding wheel rotating at a selected speed and engaging the seating face of the valve at the proper bevel angle while the valve is rotating, at a selected speed, preferably in a direction opposite to the rotation of the grinding wheel.
During the grinding operation, the maintenance of the length of the valve between the valve head surface and the distal end, the bevel angle, non-distortion of the valve, the relative constant speed and direction of rotation of the valve against the grinding wheel are important in order to be able to obtain a proper finish on the valve seat face and to prevent run-out of the valve. Run-out is the difference in concentricity along the axis of the machined surface of the valve head and the valve stem. In the prior art various machines have been patented to address these concerns. The Willemsen, et al patent U.S. No. 4,428,160 uses three rollers, two of which are driven, to rotate the valve and provide a part of the clamping function. The Willemsen device uses a separate air driven hold down member to provide a clamping action on the valve stem. The Amundsen U.S. Pat. No. 5,070,653 device uses a drive wheel for rotating the valve stem forcing the valve into the V-block supports and drawing the seating face into contact with the grinding wheel. The Wagor, U.S. Pat. No. 4,228,621 and this Applicant's Assignee's U.S. Pat. No. 4,930,261 devices show the valve being gripped on one end by a driven chuck. The Serdi Corp., U.S.A. shows in its sales literature, a valve refacing machine that vertically supports the valve stem and rotates the valve by driving the valve with a frictional pad on the valve head's surface. Another method of securing and driving the valve in a grinding device is to pull the valve stem against two spaced apart supports relying on friction to maintain the valve's position during the grinding operation.
The prior art devices rely on maintaining the valve in the proper grinding position by using the valve rotating means as a part of the valve clamping device, such as in the Willemsen and Amundsen devices and the last described method in the prior paragraph or one end or the other of the valve is driven to provide rotation and/or clamping as in the Wagor, Applicant's Assignee and Serdi disclosures. Those prior art devices, in addressing one problem, create other problems such as drawing the valve sideways or moving the valve out of its support cradle during the grinding operation.